Stellar Gravitational Lens Engineering for Interstellar Communication and Artifact SETI


A schematic of a on-axis stellar relay transmission system, opening angles, distances, and sizes not to scale. The initial unfocused transmission beam may even have an annular pattern to prevent flux from being lost to the disk of the Sun. A reversed arrangement can be used to receive signals from a distant star by focusing rays onto the spacecraft. With a total system gain of ∼ 120 dB, the outgoing beam can have an opening angle approaching 100 as described in Section 2, hundreds of times finer than the typical signal cone of a radio dish.

Several recent works have proposed "stellar relay" transmission systems in which a spacecraft at the focus of a star's gravitational lens achieves dramatic boosts in the gain of an outgoing or incoming interstellar transmission.

We examine some of the engineering requirements of a stellar relay system, evaluate the long-term sustainability of a gravitational relay, and describe the perturbations and drifts that must be actively countered to maintain a relay-star-target alignment. The major perturbations on a relay-Sun-target alignment are the inwards gravity of the Sun and the reflex motion of the Sun imparted by the planets. These approx. m/s/yr accelerations can be countered with modern propulsion systems over century-long timescales. This examination is also relevant for telescope designs aiming to use the Sun as a focusing element.

We additionally examine prospects for an artifact SETI search to observe stellar relays placed around the Sun by an extraterrestrial intelligence and suggest certain nearby stars that are relatively unperturbed by planetary systems as favorable nodes for a stellar relay communications system.

Stephen Kerby, Jason T. Wright

Comments: 13 pages, 1 figure, 2 tables
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Popular Physics (physics.pop-ph)
Cite as: arXiv:2109.08657 [astro-ph.IM] (or arXiv:2109.08657v1 [astro-ph.IM] for this version)
Submission history
From: Stephen Kerby
[v1] Fri, 17 Sep 2021 17:29:44 UTC (501 KB)
https://arxiv.org/abs/2109.08657
Astrobiology, SETI,

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